It is a second hand EGR valve. I was having the same fault code with my last EGR. The old EGR totaly packed in and i had to replace it. When i removed the old EGR valve I noticed the one of the threads on the valve was cross thread so the EGR housing wasn't sitting on the inlet manifold tight. I fixed this but still the same fault code is popping up.

I can't activate the EGR with my scan tool, just graph it. I have put the results of which on my first post.

You said whilst i've got it appart. it is a sealed unit. Isn't it?